The present invention relates to an engine control apparatus for controlling an intake air flow based on torque or a fuel injection amount, particularly to an engine control apparatus which can obtain suitable air/fuel ratio in any operating conditions.
The typical engine control apparatus is disclosed, for example, in Japanese Patent Application Laid-Open No. 7-301139 (1995).
In the prior art, the fuel injection is performed after at least two parameters is selected among the timing of the fuel injection, the ratio of air to fuel (A/F ratio), the timing of ignition and the air flow, based on the target torque calculated according to the operating condition, and thereby controlling the engine so as to improve the fuel consumption and the feeling of run.
However, the above prior art does not disclose the timing of the fuel injection and air intake. Therefore, in particular, there is a fear that the variation of the A/F ratio and the deterioration of driving feeling or exhaust occurs, owing to the response delay of air intake against the fuel injection in the transient state of the intake air flow control performed based on the torque or the fuel injection amount.
An object of the present invention is to suppress the variation of the A/F ratio and the deterioration of driving feeling or exhaust owing to the response delay of air intake against the fuel injection, in an engine control apparatus for controlling an intake air flow based on the torque or the fuel injection amount.
The above object is attained by fitting the phase of fuel injection to that of air intake. In order to fit the phase of fuel injection to that of air intake, the present invention adopts a method of delaying the fuel injection or a method of speeding up the air intake.
In the former method, time-filtering for the fuel injection amount is performed.
Concretely, an engine control apparatus according to an embodiment of the present invention has a means for calculating the width of a reference pulse used as the reference when a fuel injection pulse width is calculated based on operating conditions, a means for calculating the target A/F ratio based on the operating conditions, a means for calculating the target throttle opening based on the operating condition including the target A/F ratio, and a fuel injection phase correcting means for calculating the width of a filtering reference pulse by time-filtering the reference pulse width.
The fuel injection amount is calculated based on the filtering reference pulse width and the fuel injection control is performed.
In the latter method, an electronically controlled throttle is used to control the intake air flow. Further, the feedback constant is controlled when feedback-controlling the opening of the electronically controlled throttle.
Concretely, an engine control apparatus according to another embodiment of the present invention has a means for calculating the width of a reference pulse used as the reference when a fuel injection pulse width is calculated based on operating conditions, a means for calculating the target A/F ratio based on the operating conditions, a means for calculating the target throttle opening based on the operating condition including the target A/F ratio. Further, the target throttle opening calculating means includes a means for calculating or detecting a cylinder intake air flow, a means for calculating the target air flow, a means for feedback-calculating the target throttle opening by using the feedback control in which the cylinder intake air flow is allowed to follow the target air flow, and a means for setting the feedback constant of the target throttle opening feedback calculating means in accordance with the operating condition.
While the variation of the fuel injection amount is reflected instantaneously on the fuel injection apparatus in the transient state of the engine control apparatus which controls the intake air flow based on the torque or the fuel injection amount, the variation of the cylinder intake air flow is behind the variation of the fuel injection amount owing to the time lag required to pass through the intake pipe or the time lag necessary for the variation of the inner pressure of the intake pipe.
With regard to the above problem, in the case that the time-filtering is applied to the fuel injection amount, or the electronically controlled throttle is used for the control of the intake air flow and further the opening of the electronically controlled throttle is feedback-controlled, it becomes possible to fit the phases of the fuel injection and the air intake to each other, and thus suppress the variation of the A/F ratio and the deterioration of the drive feeling or exhaust.